+ Some terminals support more than the eight (8) "ANSI" colors. There
+ are no standard names for those additional colors.
+
+
+</PRE><H2><a name="h2-VARIABLES">VARIABLES</a></H2><PRE>
+
+</PRE><H3><a name="h3-COLORS">COLORS</a></H3><PRE>
+ is initialized by <B>start_color</B> to the maximum number of colors the ter-
+ minal can support.
+
+
+</PRE><H3><a name="h3-COLOR_PAIRS">COLOR_PAIRS</a></H3><PRE>
+ is initialized by <B>start_color</B> to the maximum number of color pairs the
+ terminal can support.
+
+
+</PRE><H2><a name="h2-FUNCTIONS">FUNCTIONS</a></H2><PRE>
+
+</PRE><H3><a name="h3-start_color">start_color</a></H3><PRE>
+ The <B>start_color</B> routine requires no arguments. It must be called if
+ the programmer wants to use colors, and before any other color manipu-
+ lation routine is called. It is good practice to call this routine
+ right after <B>initscr</B>. <B>start_color</B> does this:
+
+ <B>o</B> It initializes two global variables, <B>COLORS</B> and <B>COLOR_PAIRS</B> (re-
+ spectively defining the maximum number of colors and color-pairs
+ the terminal can support).
+
+ <B>o</B> It initializes the special color pair <B>0</B> to the default foreground
+ and background colors. No other color pairs are initialized.
+
+ <B>o</B> It restores the colors on the terminal to the values they had when
+ the terminal was just turned on.
+
+ <B>o</B> If the terminal supports the <B>initc</B> (<B>initialize_color</B>) capability,
+ <B>start_color</B> initializes its internal table representing the red,
+ green, and blue components of the color palette.
+
+ The components depend on whether the terminal uses CGA (aka "ANSI")
+ or HLS (i.e., the <B>hls</B> (<B>hue_lightness_saturation</B>) capability is
+ set). The table is initialized first for eight basic colors
+ (black, red, green, yellow, blue, magenta, cyan, and white), using
+ weights that depend upon the CGA/HLS choice. For "ANSI" colors the
+ weights are <B>680</B> or <B>0</B> depending on whether the corresponding red,
+ green, or blue component is used or not. That permits using <B>1000</B>
+ to represent bold/bright colors. After the initial eight colors
+ (if the terminal supports more than eight colors) the components
+ are initialized using the same pattern, but with weights of <B>1000</B>.
+ SVr4 uses a similar scheme, but uses <B>1000</B> for the components of the
+ initial eight colors.
+
+ <B>start_color</B> does not attempt to set the terminal's color palette to
+ match its built-in table. An application may use <B>init_color</B> to al-
+ ter the internal table along with the terminal's color.
+
+ These limits apply to color values and color pairs. Values outside
+ these limits are not legal, and may result in a runtime error:
+
+ <B>o</B> <B>COLORS</B> corresponds to the terminal database's <B>max_colors</B> capabili-
+ ty, (see <B><A HREF="terminfo.5.html">terminfo(5)</A></B>).
+
+ <B>o</B> color values are expected to be in the range <B>0</B> to <B>COLORS-1</B>, inclu-
+ sive (including <B>0</B> and <B>COLORS-1</B>).
+
+ <B>o</B> a special color value <B>-1</B> is used in certain extended functions to
+ denote the <I>default</I> <I>color</I> (see <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>).
+
+ <B>o</B> <B>COLOR_PAIRS</B> corresponds to the terminal database's <B>max_pairs</B> capa-
+ bility, (see <B><A HREF="terminfo.5.html">terminfo(5)</A></B>).
+
+ <B>o</B> legal color pair values are in the range <B>1</B> to <B>COLOR_PAIRS-1</B>, inclu-
+ sive.
+
+ <B>o</B> color pair <B>0</B> is special; it denotes "no color".
+
+ Color pair <B>0</B> is assumed to be white on black, but is actually what-
+ ever the terminal implements before color is initialized. It can-
+ not be modified by the application.
+
+
+</PRE><H3><a name="h3-has_colors">has_colors</a></H3><PRE>
+ The <B>has_colors</B> routine requires no arguments. It returns <B>TRUE</B> if the
+ terminal can manipulate colors; otherwise, it returns <B>FALSE</B>. This rou-
+ tine facilitates writing terminal-independent programs. For example, a
+ programmer can use it to decide whether to use color or some other
+ video attribute.
+
+
+</PRE><H3><a name="h3-can_change_color">can_change_color</a></H3><PRE>
+ The <B>can_change_color</B> routine requires no arguments. It returns <B>TRUE</B> if
+ the terminal supports colors and can change their definitions; other,
+ it returns <B>FALSE</B>. This routine facilitates writing terminal-indepen-
+ dent programs.
+
+
+</PRE><H3><a name="h3-init_pair">init_pair</a></H3><PRE>
+ The <B>init_pair</B> routine changes the definition of a color-pair. It takes
+ three arguments: the number of the color-pair to be changed, the fore-
+ ground color number, and the background color number. For portable ap-
+ plications:
+
+ <B>o</B> The first argument must be a legal color pair value. If default
+ colors are used (see <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>) the upper limit is ad-
+ justed to allow for extra pairs which use a default color in fore-
+ ground and/or background.
+
+ <B>o</B> The second and third arguments must be legal color values.
+
+ If the color-pair was previously initialized, the screen is refreshed
+ and all occurrences of that color-pair are changed to the new defini-
+ tion.
+
+ As an extension, ncurses allows you to set color pair <B>0</B> via the <B>as-</B>
+ <B><A HREF="assume_default_colors.3X.html">sume_default_colors(3X)</A></B> routine, or to specify the use of default col-
+ ors (color number <B>-1</B>) if you first invoke the <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B>
+ routine.
+
+
+</PRE><H3><a name="h3-init_extended_pair">init_extended_pair</a></H3><PRE>
+ Because <B>init_pair</B> uses signed <B>short</B>s for its parameters, that limits
+ color-pairs and color-values to 32767 on modern hardware. The exten-
+ sion <B>init_extended_pair</B> uses <B>int</B>s for the color-pair and color-value,
+ allowing a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-init_color">init_color</a></H3><PRE>
+ The <B>init_color</B> routine changes the definition of a color. It takes
+ four arguments: the number of the color to be changed followed by three
+ RGB values (for the amounts of red, green, and blue components).
+
+ <B>o</B> The first argument must be a legal color value; default colors are
+ not allowed here. (See the section <B>Colors</B> for the default color
+ index.)
+
+ <B>o</B> Each of the last three arguments must be a value in the range <B>0</B>
+ through <B>1000</B>.
+
+ When <B>init_color</B> is used, all occurrences of that color on the screen
+ immediately change to the new definition.
+
+
+</PRE><H3><a name="h3-init_extended_color">init_extended_color</a></H3><PRE>
+ Because <B>init_color</B> uses signed <B>short</B>s for its parameters, that limits
+ color-values and their red, green, and blue components to 32767 on mod-
+ ern hardware. The extension <B>init_extended_color</B> uses <B>int</B>s for the col-
+ or value and for setting the red, green, and blue components, allowing
+ a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-color_content">color_content</a></H3><PRE>
+ The <B>color_content</B> routine gives programmers a way to find the intensity
+ of the red, green, and blue (RGB) components in a color. It requires
+ four arguments: the color number, and three addresses of <B>short</B>s for
+ storing the information about the amounts of red, green, and blue com-
+ ponents in the given color.
+
+ <B>o</B> The first argument must be a legal color value, i.e., <B>0</B> through
+ <B>COLORS-1</B>, inclusive.
+
+ <B>o</B> The values that are stored at the addresses pointed to by the last
+ three arguments are in the range <B>0</B> (no component) through <B>1000</B>
+ (maximum amount of component), inclusive.
+
+
+</PRE><H3><a name="h3-extended_color_content">extended_color_content</a></H3><PRE>
+ Because <B>color_content</B> uses signed <B>short</B>s for its parameters, that lim-
+ its color-values and their red, green, and blue components to 32767 on
+ modern hardware. The extension <B>extended_color_content</B> uses <B>int</B>s for
+ the color value and for returning the red, green, and blue components,
+ allowing a larger number of colors to be supported.
+
+
+</PRE><H3><a name="h3-pair_content">pair_content</a></H3><PRE>
+ The <B>pair_content</B> routine allows programmers to find out what colors a
+ given color-pair consists of. It requires three arguments: the color-
+ pair number, and two addresses of <B>short</B>s for storing the foreground and
+ the background color numbers.
+
+ <B>o</B> The first argument must be a legal color value, i.e., in the range
+ <B>1</B> through <B>COLOR_PAIRS-1</B>, inclusive.
+
+ <B>o</B> The values that are stored at the addresses pointed to by the sec-
+ ond and third arguments are in the range <B>0</B> through <B>COLORS</B>, inclu-
+ sive.
+
+
+</PRE><H3><a name="h3-extended_pair_content">extended_pair_content</a></H3><PRE>
+ Because <B>pair_content</B> uses signed <B>short</B>s for its parameters, that limits
+ color-pair and color-values to 32767 on modern hardware. The extension
+ <B>extended_pair_content</B> uses <B>int</B>s for the color pair and for returning
+ the foreground and background colors, allowing a larger number of col-
+ ors to be supported.
+
+
+</PRE><H3><a name="h3-reset_color_pairs">reset_color_pairs</a></H3><PRE>
+ The extension <B>reset_color_pairs</B> tells ncurses to discard all of the
+ color-pair information which was set with <B>init_pair</B>. It also touches
+ the current- and standard-screens, allowing an application to switch
+ color palettes rapidly.
+
+
+</PRE><H3><a name="h3-PAIR_NUMBER">PAIR_NUMBER</a></H3><PRE>
+ <B>PAIR_NUMBER(</B><I>attrs</I>) extracts the color value from its <I>attrs</I> parameter
+ and returns it as a color pair number.
+
+
+</PRE><H3><a name="h3-COLOR_PAIR">COLOR_PAIR</a></H3><PRE>
+ Its inverse <B>COLOR_PAIR(</B><I>n</I><B>)</B> converts a color pair number to an attribute.
+ Attributes can hold color pairs in the range 0 to 255. If you need a
+ color pair larger than that, you must use functions such as <B>attr_set</B>
+ (which pass the color pair as a separate parameter) rather than the
+ legacy functions such as <B>attrset</B>.
+
+
+</PRE><H2><a name="h2-RETURN-VALUE">RETURN VALUE</a></H2><PRE>
+ The routines <B>can_change_color</B> and <B>has_colors</B> return <B>TRUE</B> or <B>FALSE</B>.
+
+ All other routines return the integer <B>ERR</B> upon failure and an <B>OK</B> (SVr4
+ specifies only "an integer value other than <B>ERR</B>") upon successful com-
+ pletion.
+
+ X/Open defines no error conditions. SVr4 does document some error con-
+ ditions which apply in general:
+
+ <B>o</B> This implementation will return <B>ERR</B> on attempts to use color values
+ outside the range <B>0</B> to <B>COLORS</B>-1 (except for the default colors ex-
+ tension), or use color pairs outside the range <B>0</B> to <B>COLOR_PAIRS-1</B>.
+
+ Color values used in <B>init_color</B> must be in the range <B>0</B> to <B>1000</B>.
+
+ An error is returned from all functions if the terminal has not
+ been initialized.
+
+ An error is returned from secondary functions such as <B>init_pair</B> if
+ <B>start_color</B> was not called.
+
+ <B>o</B> SVr4 does much the same, except that it returns <B>ERR</B> from <B>pair_con-</B>
+ <B>tent</B> if the pair was not initialized using <B>init_pairs</B> and it re-
+ turns <B>ERR</B> from <B>color_content</B> if the terminal does not support
+ changing colors.
+
+ This implementation does not return <B>ERR</B> for either case.
+
+ Specific functions make additional checks:
+
+ <B>init_color</B>
+ returns an error if the terminal does not support this feature,
+ e.g., if the <B>initialize_color</B> capability is absent from the
+ terminal description.
+
+ <B>start_color</B>
+ returns an error if the color table cannot be allocated.
+
+
+</PRE><H2><a name="h2-NOTES">NOTES</a></H2><PRE>
+ In the <B>ncurses</B> implementation, there is a separate color activation
+ flag, color palette, color pairs table, and associated <B>COLORS</B> and <B>COL-</B>
+ <B>OR_PAIRS</B> counts for each screen; the <B>start_color</B> function only affects
+ the current screen. The SVr4/XSI interface is not really designed with
+ this in mind, and historical implementations may use a single shared
+ color palette.
+
+ Setting an implicit background color via a color pair affects only
+ character cells that a character write operation explicitly touches.
+ To change the background color used when parts of a window are blanked
+ by erasing or scrolling operations, see <B><A HREF="curs_bkgd.3X.html">curs_bkgd(3X)</A></B>.
+
+ Several caveats apply on older x86 machines (e.g., i386, i486) with
+ VGA-compatible graphics:
+
+ <B>o</B> COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW
+ combined with the <B>A_BOLD</B> attribute.
+
+ <B>o</B> The A_BLINK attribute should in theory cause the background to go
+ bright. This often fails to work, and even some cards for which it
+ mostly works (such as the Paradise and compatibles) do the wrong
+ thing when you try to set a bright "yellow" background (you get a
+ blinking yellow foreground instead).
+
+ <B>o</B> Color RGB values are not settable.
+
+
+</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
+ This implementation satisfies XSI Curses's minimum maximums for <B>COLORS</B>
+ and <B>COLOR_PAIRS</B>.
+
+ The <B>init_pair</B> routine accepts negative values of foreground and back-
+ ground color to support the <B><A HREF="default_colors.3X.html">use_default_colors(3X)</A></B> extension, but only
+ if that routine has been first invoked.
+
+ The assumption that <B>COLOR_BLACK</B> is the default background color for all
+ terminals can be modified using the <B><A HREF="default_colors.3X.html">assume_default_colors(3X)</A></B> exten-
+ sion.
+
+ This implementation checks the pointers, e.g., for the values returned
+ by <B>color_content</B> and <B>pair_content</B>, and will treat those as optional pa-
+ rameters when null.
+
+ X/Open Curses does not specify a limit for the number of colors and
+ color pairs which a terminal can support. However, in its use of <B>short</B>
+ for the parameters, it carries over SVr4's implementation detail for
+ the compiled terminfo database, which uses signed 16-bit numbers. This
+ implementation provides extended versions of those functions which use
+ <B>short</B> parameters, allowing applications to use larger color- and pair-
+ numbers.
+
+ The <B>reset_color_pairs</B> function is an extension of ncurses.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <B><A HREF="curses.3X.html">curses(3X)</A></B>, <B><A HREF="curs_initscr.3X.html">curs_initscr(3X)</A></B>, <B><A HREF="curs_attr.3X.html">curs_attr(3X)</A></B>, <B><A HREF="curs_variables.3X.html">curs_variables(3X)</A></B>, <B>de-</B>
+ <B><A HREF="default_colors.3X.html">fault_colors(3X)</A></B>